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241.
双频光栅轮廓术的研究 总被引:5,自引:0,他引:5
在投影栅相位法轮廓检测中,当物体含突变部分时,包裹相位很难准确恢复,对此可用双频变精度技术来解决。如果用两种不同频率光栅分两次进行测量,无疑增加了测量负担,也无法满足实时检测的要求。提出用软件生成两种不同频率成分的复合正弦光栅,用液晶投影仪投影,针对不同物体具体突变部分的情况,可灵活生成各种不同灵敏度的复合光栅。只采一次图像就可以达到以往双频技术中多次采集的效果,该法具有快速和去包裹精度高的特点。最后,进行了实验测试,结果非常满意。 相似文献
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Improved holographic particle sizing by using absolute values of the wavelet transform 总被引:3,自引:0,他引:3
A new method for sizing particle from in-line particle holograms by using absolute values of the wavelet transform is proposed in order to improve accuracy in measurements. The proposed method provides direct calculation of the particle size by using spatial frequency information of a chirp signal at minima position of an envelope function. Simulation and experimental results are presented. 相似文献
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In order to utilize the space of an input plane efficiently and make the optical structure more flexible, an image displacement measurement based on phase-encoded reference joint fractional transform correlator (PER-JFrTC) is proposed. We use a random phase mask to encode the reference image and overlay it with the target image forming the input image. Joint power spectrum (JPS) of the input image is obtained by Fourier transform and the resultant is encoded by the same phase mask. Then a fractional Fourier transform with an order p is applied to the phase-encoded JPS (PJPS), resulting in a correlation output with a sharp cross-correlation peak, which includes the displacement information between the reference and the target image. Contrast to displacement measurement based on traditional joint transform correlator (JTC), PER-JFrTC can use the space of the input plane efficiently and reduces the influence of the auto-correlation. Also the position of cross-correlation peak can be fixed arbitrarily according to the fractional order p as well as the optical set-up can be more flexible and easier to implement. Results based on digital computation show that PER-JFrTC could detect the displacement accurately and verify our proposal. A possible optical set-up is suggested. 相似文献
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Based on the newly constructed two mutually conjugate 3-mode entangled states of continuum variablesin three-mode Fock space we introduce entangled fractional Fourier transform (EFFT) for the tripartite entangled staterepresentations, which are not a direct product of three 1-dimensional FFTs. The eigenmodes of EFFT are obtained,which is different from the usual Hermite polynomials. The EFFT of the three-mode squeezed state is derived. 相似文献
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Zhang Guangzhao Zhou Guangqun 《International Journal of Infrared and Millimeter Waves》1989,10(2):257-267
The Marple algorthm for the autoregressive spectral estimates has been applied to the SMMW Fourier transform spectrum analysis. The experimental results have shown that this method yields AR spectra with three times higher resolution than the FFT method does. The improvements obtained from the Marple algorithm over the maximum entropy algorithm include higher resolution, less bias in the spectral peak frequency estimation and absence of observed spectral line splitting. The effects of the structure of the spectral lines and the noise on the resolution are discussed.Projects supported by National Natural Science Foundation of China 相似文献
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